Esters of sulfenic acids and their preparation



United States Patent ESTERSOF SWEENIC AIDS AND THEIR 5 PREPARATION Norman Kharasch, (3'ulver ity, Califi, assignor to Stautfer Chemical Company, a corporation of Deiaware No Drawing, Application April-2, 1956 Serial No. 575,356.

18-Clain1s. (Cl. 2609-456) where R represents any alkyl or aryl group, ROH is any alcohol, and X is a h'alogen,e. g., chlorine and bromine, this reaction proceeds with diificulty, if at all. For example, even in rigorouslydry alcohol, in many cases, the disulfides are the major product. With methanol, for instance, an-8090% yield of-disulfide is obtained when reacted withp-chlorobenzenesulfenyl chloride; Also, 2- n'itrobenzenesulfenyl chloride on alcoholysis gives such products as Z-nitrophenyl-Z nitrobenzenethiolsulfonate, Z-nitrobenzenesulfinic acid and the disulfide. 2,4-dinitrobenzenesulfenylchloride reacts with dry methanol or ethanol to give reasonable yields of the, ester, but with a tertiary alkyl alcohol no ester at all-was obtained.

I have-found that arylsulfenyl chlorides and alkylsulfenyl chlorides react smoothly with an alcohol in the presence ofa tertiary amine to give the corresponding sulfenates in high yields. That tertiary amines are effec tive in activating this reaction was surprising since it had been earlier reported by M. L. Moore and T. B. Johnson (J 4 Chemi Soc., 57, 1517,1935) that sulfenyl halides react-with drypyridine to form disulfides. The use of tertiary amines was found to be very general and applicable in this'reaction toa wide variety of alcohols. It is essential for the preparation of sulfenates of tertiary alcohols-whichcan be reacted'in' high yield by this method.

Pyridine is particularly effective, while acridineand triethylamin'ealso give excellent yields. The presence of tertiary amine should be present in substantial amount and I prefer'to use at leastabout one molecular equivalent to-ensure that the-reaction proceeds satisfactorily. An excess of tertiary amine is neither a' detriment. nor an advantage. If. wetreagents are used, the esters are obtained in somewhat reduced yield.

The sulfenate esters of the present invention are useful in many different applications. For example, the tertiary alkyl 2,4-dinitrobenzenesulfenates are particularly useful as inhibitors for the stabilization of vinyl monomers. They have the property of decomposing in the range of 100-l25 C., with a resulting change in inhibitory power. This is useful where it is desired to leave the inhibitor in the monomer during polymerization and yet protect the monomer prior to polymerization.

The various sulfenate esters are also useful chemical intermediates. For example, heating methyl 2,4-dinitrobenzenesulfenate with aqueous hydrochloric acid gives 2-amino-4-nitrobenzenesulfonic acid, a useful dye intermediate. The alkyl trichloromethanesulfenates can be H oxidized in stages to alkyl trichloromethanesulfenates and alkyl trichloromethanesulfonates which have heretofore been unobtainable by conventional methods.

2. The esters of trichloromethanesulfenic acid, listedin Table II, also have various other uses, e. g., they are particularly effective in the formulation of pesticide compositions, for herbicidal and fungicidal applications, the esters being active herbicides and fungicides.

The esters of trichloromethanesulfenic acid are generally sufliciently stable to distill at low or somewhat'reduced pressures. However, when the esters areheated to a temperature approaching their normal boiling points,- the esters decompose in a free-radical manner and, under certain conditions, have been found to be highly explosive. In this respect, they areakin to peroxides (RSOR vs. ROOR'). Because of these properties, the alkyl and substituted alkyl trichloromethanesulfenates are useful for initiating and modifyingthe course of vinyl polymerizations. The pharmaceutical properties of sterol derivatives such as the testosterones, are well-known; and'it is also known that various derivatives of thesesubstances arephysiologically potent. The sulfenate esters derived from the sterols arealso useful chemotherapeutic agents The long chain alkyl esters, such as the octadecyl' esters, have properties which make them useful-inthe formulation of Waxes and in paper formulations where their fun; gicidal properties are also useful.

Other esters oftrichloromethanesulfenic acid are valuable in improving the ignition qualities of diesel oil and aslubricating oil additives.

To illustrate preparation of materials involving the present invention, the following'operation is set forth:

To a dry SO-ml. Erlenmeyer flask, there was added 10 ml. of ethylene chloride and 1.0g. of 2,4-dinitrobenzenesulfenyl chloride. The mixturewasswirled and heated gently to effect solution; then the alcohol (1 m1. ofliquid or 1 g. of'solid) was added, the'flask'again'swirled, and 1 ml. of pyridine added. A distinct deepening-of the yellow color was generally observed as the pyridine dissolved in the solution; and, in some cases, a white, needlelike precipitate (probably pyridine hydrochloride) was noted. The reaction appears to be complete immediately after adding the pyridine (negative test With starchiodide paper or solution); but the reaction mixture was swirled and let stand 15-30 minutes to assure precipitation of any insoluble residue which may'have formed. Themixture was filtered, and the residue-washed on the filter plate with a few ml. of hot ethylene chloride. The bright yellow residue, the amount ofwhich varied, with the alcohol used and being from 0T15%. of the total weight of sul-fenate ester obtained, was discardedg'the filtrate was aspirated to dryness with-a water-pump at room temperature. The residue from the'filtratewas-extracted with three to five 10 ml. portions of cold water, and the crude sulfenate ester collected and'air-dried on the suction filter plate. After further drying in the vacuum desiccator (charged with calcium sulfate), or in the heating pistol at 56 (acetone), the crude products" were recrystallized from hotabsolute ethanol; or, in some cases; from alcohol-benzene mixtures. If the crude products were washed well and dried, the melting points were generally within a few degrees of the purified samples. The results obtained by this method are given in Table I with respect to various typical aryl compounds embodying the present invention. In the main, these examples represent esters of 2,4-dinitrobenzenesulfenic acid.

The alkyl esters set forth in Table II were prepared by the method set forth above, but the compounds were purified by distillation rather than by a crystallization technique as in the case of the aryl compounds.

In the case of the trichloromethanesulfenates, the reaction mixture was generally allowed to stand for several hours or over-night, to ensure completeness of reaction. An example is as follows: One mole, 186 g., of trichloromethanesulfenyl chloride was dissolved in 300 ml. of dry ethylene chloride. One mole (94.5 g.) of 1-chloro-2- propanol was then added during a period of a few minutes, with stirring, followed by 1.1 mole of dry pyridine in 50 ml. of ethylene chloride. The reaction mixture was stirred, then let stand for twelve hours, at which time the mixture gave a negative test potassium iodide-starch paper. This was thenextracted with two portions, 200 ml. each, of water, to remove pyridine hydrochloride and excess pyridine. The residue was dried over anhydrous sodium sulfate, and then distilled, to give the prodnet, in 57% yield, pure, B. P. 79-80 at 0.1 mm. mercury pressure. The product was analyzed for elementary composition, as shown in the footnote to Table II.

Table I.

Hydro- Ester 1 Yield, M. P., 0. Carbon gen percent found found 95 122-123 85 124-125 85 76-76 41. 84 3. 87 90 77-78 41. 93 4. 16 85 53-54 44. 32 4. 77 80 71-72 43. 77 4. 22 t-Butyl "1.1..-" 80 118-119 44. 39 4. 45

i hlorometh 1-din1et I- Tr c h y y 75 32. 20 2. 66 85 31-32 45. 98 5. 01 85 56-57 46. 18 5. 23 85 102-103 40. 18 4. 78 90 57-58 51.21 0. 20 85 73-74 65. 88 7. 01 85 133-134 48. 37 4. 79 90 98-99 85 99-100 54. 33 6. 21 95 142-143 51. 13 3. 41 75 113. -114 36. 77 3. 18 91 170-171 5 30. 71 2. 20 33 133. 5-135 42. 50 3. 53 93 92-93 52. 59 3. 77 14 86-87 42. 28 3. 28 35 120-123 54. 41 3. 79 29 113 60. 31 3. 07 80 53 53. 20 5. 48 70 122-124 49. 6 3.01 70 199-200 60. 71 5. 78 Testosteronyl 66 204. 5-205 5 61.91 5.84 17-methy1 testosteronyl 70 170-17 62. 65 0. 56 Methyl 12-nitrobenzene ienate 80 51-52 N ,n-dimethylaminoethyl 90 73-74 42. 20 4. 65

1 Of 2,4-dinltrobenzene sulienic acid unless otherwise stated.

. Table II Ester 1 Yield 2 Boiling point/mm. m

Beta-me yethyL- Betahenox eth l. Tetra ydrof rlurgi. 74.575.5/0.2 mm.. 1. 5180 1-chioro-2-propyl 47-48/0.15 mm 1. 5106 1,3-dichIoro-2-propyl 79-80/O.1 mm 1. 5320 I Ester of trichloromethanesulfenic acid.

1 0t pure product. Crude yields -20% higher.

I Analysis for sulfur: Found, S=15.52; the0ry=15.4.

4 Analysis: Found for Ol=63.72; for carbo11=17.02; 1o ydr gen=1.50;

r forsuliur=11.65. Theory: Cl=63.70;0=17.2; H=1.79; S=11.

4 I claim: 1. Chemical compounds having the formula:

' CCl SOR wherein R is selected from the group consisting of lower alkyl, chloro-substituted lower alkyl, allyl, tetrahydrofurfuryl, beta-methoxyethyl and beta-phenoxyethyl radicals.

. Beta-chloroethyl trichloromethanesulfenate.

. T-butyl trichloromethanesulfenate.

. Allyl trichloromethanesulfenate.

. l-chloro-Z-propyl trichloromethanesulfenate.

. 1,3-dichloro-2-propyl trichloromethanesulfenate.

The process of preparing an ester of sulfenic acid which comprises reacting a sulfenyl halide selected from the group consisting of an aromatic sulfenyl halide and an aliphatic sulfenyl halide with an alcohol in the presence of a tertiary amine.

8. The process of preparing esters of alkylsulfenic acids which comprises reacting an alkylsulfenyl chloride, was an alcohol in the presence of a tertiary amine.

9. The process of preparing esters of alkylsulfenic acids which comprises reacting an alkylsulfenyl chloride with an alcohol in the presence of oneor more molecular equivalents of a tertiary amine based on the sulfenyl chloride.

10. The process of esterification as described in claim 8 wherein the tertiary amine is pyridine.

11. The process of esterification as described in claim 8 wherein the alkylsulfenyl chloride is trichloromethane-t sulfenyl chloride.

12. The process of preparing an ester of a sulfenic acid which comprises reacting a sulfenyl halide with an alcohol in the presence of a tertiary amine.

13. The process of preparing an ester of a sulfenic acid which comprises reacting a sulfenyl halide selected from the group consisting of an aryl sulfenyl halide and an alkyl sulfenyl halide with an alcohol in the presence of a tertiary amine.

14. The process of preparing esters of arylsulfenic acids which comprises reacting an arylsulfenyl halide with an alcohol in the presence of a tertiary amine.

15. The process of preparing esters of arylsulfenic acids which comprises reacting an arylsulfenyl halide with an alcohol in the presence of one or more molecular equivalents of a tertiary amine based on the arysulfenyl halide.

16. The process of esterification as described in claim 15 wherein the tertiary amine is pyridine.

17. The process of esterification as described in claim 15 wherein the arylsulfenyl halide is 2,4-dinitrobenzenesulfenyl chloride and the tertiary amine is pyridine.

18. The process of esterification as described in claim 17 wherein the alcohol is tertiary-butyl alcohol.

References Cited in the file of this patent Kharasch et al.: Chemical Reviews, vol. 39 (1946), pp. 323-327.

Perold et al.: Iour. Am. Chem. Soc., vol 73 (1951), p. 2380. 

1. CHEMICAL COMPOUNDS HAVING THE FORMULA:
 7. THE PROCESS OF PREPARING AN ESTER OF SUFFENIC ACID WHICH COMPRISES REACTING A SULFENYL BALIDE SELECTED FROM THE GROUP CONSISTING OF AN AROMATIC SULFENLY HALIDE AND AN ALIPHATIC SULFENYL HALIDE WITH AN ALCOHOL IN THE PRESENCE OF A TERTIARY AMINE. 